It's likely to be possible to go to 3650 as a paper exercise but you need to get SV tech or VWE to confirm. But as my edit above says you may really need more allowance on the rear axle than 1900 but you will only know this by going to a weighbridge fully laden as others have said. I would do this first as only you know how you will load up your van.So is this something that’s possible as an up plate ? Is that how they work out the max weight I thought it was a lot of high tech working out stuff .